A listing on the Xbox 360 marketplace may have inadvertently revealed one of the first pieces of downloadable content for upcoming sci-fi role-playing game Mass Effect 3 — and spoiled a plot point from the game.

Warning: Minor spoilers about the nature of one of the game's DLC packs follow.

Mass Effect 3: From Ashes, released February 20 presumably by accident, will apparently allow players to "unearth lost secrets from the past" and enlist a member of the game's Prothean race (confirming previous rumors).

When Kotaku tried to download the DLC pack, we received an error message saying, "Cannot retrieve information from Xbox LIVE."

Update: BioWare Associate Producer Michael Gamble took to the company's official forums to address the leak:

Hi all!

We're happy to confirm that Mass Effect 3: From Ashes DLC will be available at launch for all platforms. For those of you who have purchased the N7 Collector's Edition (including the PC Digital Deluxe Edition), you will get this content at no extra charge. We'll have a lot more details for you later this week! Stay Tuned!